The present invention relates generally to semiconductor device manufacturing and more specifically to a method and apparatus for heating and cooling substrates.
Semiconductor wafers, flat panel displays and other similar substrates typically have numerous material layers deposited thereon during device fabrication. Some commonly deposited layers (e.g., spin-on glass (SOG) films) may contain contaminants, defects or undesirable microstructures that can be reduced in number or altogether removed by heating or xe2x80x9cannealingxe2x80x9d the substrate at an appropriate temperature for an appropriate time. Other deposited layers (e.g., copper films) may have properties that undesirably change over time or xe2x80x9cself-annealxe2x80x9d, resulting in unpredictable deposited layer properties (e.g., unpredictable resistivity, stress, grain size, hardness, etc.). As with contaminants, defects and undesirable microstructures, deposited layer properties often can be stabilized by a controlled annealing step (e.g., for copper films, a 200-400xc2x0 C., 15 second-3 minute anneal in a gas such as N2 or about 96% N2, 4% H2). Following any annealing step, a substrate preferably is rapidly cooled so that other processes can be performed on the substrate without delay (i.e., to increase throughput).
Conventionally annealing is performed within a quartz furnace that must be slowly pre-heated to a desired annealing temperature, or within a rapid thermal process (RTP) system that can be rapidly heated to a desired annealing temperature. Thereafter an annealed substrate is transferred to a separate cooling module which conventionally employs a cooled substrate support and is slightly backfilled with a gas such as argon to enhance thermal conduction. The separate cooling module increases equipment cost and complexity, as well as equipment footprint, and decreases substrate throughput by requiring substrate transfer time between the heating and cooling systems. Accordingly, a need exists for an improved method and apparatus for heating and cooling substrates that is less expensive, less complex, and has a reduced equipment footprint and increased throughput when compared to conventional substrate heating and cooling systems.
To overcome the needs of the prior art, an inventive chamber is provided that allows for rapid heating and cooling of a substrate within a single chamber. As no transfer time to a separate cooling module is required, the invention decreases equipment cost, complexity and footprint while increasing substrate throughput. Specifically, the inventive chamber includes a heating mechanism adapted to heat a substrate positioned proximate the heating mechanism, a cooling mechanism spaced from the heating mechanism and adapted to cool a substrate positioned proximate the cooling mechanism, and a transfer mechanism adapted to transfer a substrate between a position proximate the heating mechanism and a position proximate the cooling mechanism. As used herein xe2x80x9cproximatexe2x80x9d means close enough to affect sufficient thermal energy transfer for either heating or cooling a substrate. The heating mechanism and the cooling mechanism preferably are separated by about 1 to 5 inches.
The heating mechanism preferably comprises a heated substrate support adapted to support a substrate and to heat the supported substrate to a predetermined temperature, and the cooling mechanism preferably comprises a cooling plate (e.g., a water cooled cooling plate or a refrigerant cooled cooling plate). A plurality of holes may be provided within the cooling plate that allow a gas to flow through the cooling plate (so as to cool the gas) before the gas strikes a substrate positioned proximate the cooling plate.
The transfer mechanism transfers a substrate from a position proximate the heating mechanism to a position proximate the cooling mechanism, and preferably employs only single-axis, linear motion so as to further reduce equipment complexity and cost. The transfer mechanism may comprise, for example, a wafer lift hoop having a plurality of fingers adapted to support a substrate, or a plurality of wafer lift pins. A dry gas source may be coupled to the chamber in order to supply a dry gas thereto. The chamber includes a pump adapted to evacuate the chamber to a predetermined pressure (e.g., about 20 and 200 Torr) during cooling, as the present inventors have found that a reduced chamber pressure provides good thermal conduction for short distances (so that a substrate positioned proximate the cooling mechanism is cooled thereby) but poor thermal conduction for large distances (so that a substrate being cooled by being positioned proximate the cooling mechanism is not also heated by the distantly located heating mechanism).
As is apparent from the above description, the invention provides a method for efficiently heating (e.g., annealing, degassing, etc.) and cooling a substrate within a single chamber. Wafer transfer time is reduced, footprint is reduced and simpler wafer movements are employed.
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.